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Neptune's Moons
Prior to 1989, only two of Neptune's moons had been discovered, Triton in 1846 and Neried in 1949. Triton is one of only two moons in the solar system with a fully developed atmosphere. It's atmosphere is of chilled methane kept at -200 degrees C. Triton is one of only a few moons which are currently geologically active.
| MOON | DISCOVERY AND DATE | DIAMETER (KM) | DISTANCE FROM NEPTUNE (KM) |
| 1989N6 | Project Voyager, 1980 | 50 | 23,000 |
| 1989N5 | Project Voyager, 1989 | 90 | 25,000 |
| 1989N4 | Project Voyager, 1989 | 135 | 27,150 |
| 1989N3 | Project Voyager, 1989 | 160 | 37,100 |
| 1989N2 | Project Voyager, 1989 | 200 | 48,100 |
| 1989N1 | Project Voyager, 1989 | 420 | 92,500 |
| Triton | William Lassell, 1846 | 2700 | 329,880 |
| Nereid | Gerard Kupier, 1949 | 500 | 5,500,000 |